Actuation system for an active element in a rotor blade

ABSTRACT

In accordance with one embodiment of the present application, an actuation system is configured for actuation of an airfoil member with a flap mechanism. The actuation system can include an upper drive tape and a lower drive tape, each partially wrapped around a first bearing and second bearing. An inboard frame can be actuated by at least one linear actuator. Similarly, an outboard frame can be actuated by at least one linear actuator. The inboard frame is coupled to the upper drive tape, while the outboard frame is coupled to the lower drive tape. An actuation of the inboard frame and outboard frame in a reciprocal manner acts move a flap input lever reciprocally upward and downward. A flap mechanism is configured to convert the movement of the flap input lever into rotational movements of the airfoil member.

BACKGROUND

1. Technical Field

The present application relates to an active element actuation systemfor a rotor blade.

2. Description of Related Art

It can be desirable to implement an actively controlled aerodynamicmember on a rotor blade to improve rotor blade performance duringaircraft operation. One conventional design uses a push/pull rodconnected to a bell crank on a trailing edge flap. Such a configurationcan have several undesirable limitations. For example, the bell crankcan penetrate the profile of the rotor blade, thereby negativelyincreasing the drag. Further, rod end elements can have high coulombfriction and produce an uneven stick-slip motion. Even further, wearover time can eventually produce backlash from mechanical slop betweenthe actuator and the flap, thereby reducing controllability of the flap.Even further, conventional designs can include a potential single pointfailure, such as a ball screw on an electromechanical actuator, which issusceptible to a mechanical jam.

Hence, there is a need for an improved actuation system for an activeelement on a rotor blade.

DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the system of the presentapplication are set forth in the appended claims. However, the systemitself, as well as a preferred mode of use, and further objectives andadvantages thereof, will best be understood by reference to thefollowing detailed description when read in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a side view of an aircraft having a rotor blade with an activeflap, according to one example embodiment;

FIG. 2 is a perspective view of the rotor blade with the active flap,according to one example embodiment;

FIG. 3 is a perspective view of an actuation system and a flap mechanismfor actuating the active flap, according to one example embodiment;

FIG. 4 is a perspective view of the actuation system, according to oneexample embodiment;

FIG. 5 is an exploded view of the actuation system, according to oneexample embodiment;

FIG. 6 is a top view of the actuation system, according to one exampleembodiment;

FIG. 7 is a partial cross-sectional view of the actuation system, takenat section lines 7-7 in FIG. 6, according to one example embodiment;

FIG. 8 is a partial cross-sectional view of the actuation system, takenat section lines 8-8 in FIG. 6, according to one example embodiment;

FIG. 9 is a perspective view of the inboard frame, according to oneexample embodiment;

FIG. 10 is an exploded view of the inboard frame, according to oneexample embodiment;

FIG. 11 is a perspective view of the flap mechanism, according to oneexample embodiment;

FIG. 12 is a top view of the flap mechanism and the actuation system,according to one example embodiment; and

FIG. 13 is a partial cross-sectional view of the flap mechanism and theactuation system, taken at section lines 13-13 in FIG. 12, according toone example embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the system are described below. In theinterest of clarity, all features of an actual implementation may not bedescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedeveloper's specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

In the specification, reference may be made to the spatial relationshipsbetween various components and to the spatial orientation of variousaspects of components as the devices are depicted in the attacheddrawings. However, as will be recognized by those skilled in the artafter a complete reading of the present application, the devices,members, apparatuses, etc. described herein may be positioned in anydesired orientation. Thus, the use of terms such as “above,” “below,”“upper,” “lower,” or other like terms to describe a spatial relationshipbetween various components or to describe the spatial orientation ofaspects of such components should be understood to describe a relativerelationship between the components or a spatial orientation of aspectsof such components, respectively, as the device described herein may beoriented in any desired direction.

Referring now to FIG. 1 in the drawings, a rotorcraft 101 isillustrated. Rotorcraft 101 has a rotor system 103 with a plurality ofrotor blades 105. The pitch of each rotor blade 105 can be managed inorder to selectively control direction, thrust, and lift of rotorcraft101. Rotorcraft 101 can further include a fuselage 107, anti-torquesystem 109, and an empennage 111.

Referring now also to FIG. 2, an example rotor blade 105 is illustratedin further detail. Rotor blade 105 has a root end 102, a tip end 104, aleading edge portion 106, and a trailing edge portion 108. Each rotorblade 105 can include a flap 113 that is actively actuated by anactuation system 115. Actuation system 115 is configured to selectivelyactuate flap 113 so as to provide enhancements of over fixed rotor bladegeometry designs, such as: vibration reduction, acoustic reduction, andimproved aerodynamic performance. Actuation system 115 is lightweight,compact, wear resistant, and powerful, thereby realizing benefits of anactive rotor blade.

It should be appreciated that rotorcraft 101 is merely illustrative of awide variety of aircraft that can implement the systems disclosesherein, such as actuation system 115 for actuating an airfoil member ona rotor blade. Other aircraft implementations can include hybridaircraft, tilt rotor aircraft, unmanned aircraft, gyrocopters, and avariety of helicopter configurations, to name a few examples. Further,trailing edge flap 113 is merely illustrative of a wide variety ofmoveable airfoil members that can be actuated with actuation system 115and flap mechanism 117. For example, a leading edge droop is anotherillustrative moveable airfoil surface that can be actuated withactuation system 115. Further, it should be appreciated that a pluralityof actuation systems 115 may be employed on a single rotor blade 105.

Referring now also to FIG. 3, actuation system 115 can be operablyassociated with a flap mechanism 117. Flap mechanism 117 is configuredto receive inputs from actuation system 115 and mechanically convey theinputs to trailing edge flap 113, while also reacting centrifugal forcessubjected upon trailing edge flap 113 during operation, as discussedfurther herein. Even though flap mechanism 117 is illustrated inconjunction with actuation system 115, flap mechanism 117 can beimplemented on a rotor blade having an actuation system that isdifferent from actuation system 115.

Referring now also to FIGS. 4-8, actuation system 115 is described infurther detail. Actuation system 115 can include an inboard frame 119operably associated with linear actuators 123 a and 123 b. Similarly,actuation system 115 can include an outboard frame 121 operablyassociated with linear actuators 123 c and 123 d. It should beappreciated that an alternative embodiment of actuation system 115 caninclude a fewer or greater number of linear actuators. In the interestof clarity, linear actuator 123 a is further described; however, itshould be appreciated that linear actuators 123 b-123 d are preferablyidentical to linear actuator 123 a. Further, inboard frame 119 issubstantially similar to outboard frame 121, as such, in the interest ofclarity, redundant features between frame 119 and frame 121 may only bediscussed with regard to one or the other.

Linear actuator 123 a can include a stator 137 having a plurality ofconductive windings, and a forcer 139 having a plurality of magnets.Forcer 139 can be linearly displaced at a selected frequency andmagnitude by a control system that selectively applies a control signalto stator 137. Forcer 139 is rigidly coupled to frame 119, thus lineartranslation of forcer 139 similarly translates frame 119. It should beappreciated that linear actuator 123 a is merely illustrative of a widevariety of linear actuators that can be suitable for generating linearmotion with suitable displacement and frequency characteristics. Forexample, linear actuator 123 a can be a linear motor, pneumaticcylinder, or pneumatic muscle, to name a few.

The stator portion of linear actuator 123 a can be located in a housing141 that is configured to secure stator 137 relative to the internalstructure of rotor blade 105. Further, housing 141 can be configured asa heat sink so as to provide a conductive path for removing heatgenerated by linear actuator 123 a. As such, housing 141 is preferablymade from a heat conductive material, such as aluminum, for example.

A plurality of heat pipes 143 can used to provide efficient heattransfer from housing 141 to an exterior surface of rotor blade 105.Each heat pipe 143 includes an evaporator end 147 and a condenser end145. The evaporator end 147 is in thermal contact with housing 141.Thermal grease can be used to promote thermal contact between theevaporator end 147 and housing 141. The condenser end 145 is in athermal path with a rotor blade structure such that heat can betransferred to an exterior surface of rotor blade 105.

During operation, each heat pipe 143 transfers heat from housing 141 toan exterior surface of rotor blade 105, where the heat can dissipateinto the ambient air. Further, airflow over the exterior surface ofrotor blade 105 acts to further remove heat via convection.

Each heat pipe 143 is formed at an angle such that operationalcentrifugal forces promote condensed fluid to travel from condenser end145 to evaporator end 147. The angle in each heat pipe 143 is formed bya bend located approximately mid-length of heat pipe 143. The angle ofthe bend is configured so that condenser end 145 can approximatelyconform and have maximum contact area with the exterior surfacestructure rotor blade 105. Further, the angle of the bend in each heatpipe 143 is also configured so that evaporator end 147 can have maximumcontact area with housing 141. The thickness and camber of rotor blade105 can affect the specific angle of the bend in heat pipe 143. Forexample, a rotor blade having a small thickness between upper and lowerairfoil surfaces may have a smaller bend angle, as compared to a rotorblade having a large thickness between upper and lower airfoil surfaces.The unique location and orientation of heat pipes 143 allows for theutilization of centrifugal forces to overcome the undesirable force ofgravity and promote the return of the condensed working fluid fromcondenser end 145 to evaporator end 147.

Actuation system 115 can further include linear bearing assemblies 149a-149 d to support inboard frame 119 and outboard frame 121 against eachhousing 141 of linear actuators 123 a-123 d, while reducing frictionduring the relative linear translation therebetween. Further, eachlinear bearing assembly 149 a-149 d is configured to prevent increasedfriction due to operationally generated spanwise centrifugal forces.Even though linear bearing assemblies 149 a-149 d are illustrated, itshould be appreciated that linear actuators 123 a-123 d can be moveablysupported against frames 119 and 121 using any variety of suitableconfigurations, such a bearings, gears, slidable elements, to name a fewexamples.

Inboard frame 119 is reciprocally driven by actuators 123 a and 123 bacting in unison. If one of actuators 123 a or 123 b were to fail, theremaining healthy actuator can provide continued operation whileovercoming the slight parasitic drag of the failed actuator. Similarly,outboard frame 121 is reciprocally driven by actuators 123 c and 123 dacting in unison. However, actuation system 115 is configured such thatactuators 123 a and 123 b translate inboard frame 119 in an oppositedirection to the translation direction of outboard frame 121 byactuators 123 c and 123 d, the translations being in an oscillatorymanner, as discussed further herein.

An extension 151 of Inboard frame 119 is coupled to an upper drive tape125. Similarly, an extension 153 of outboard frame 121 is coupled to alower drive tape 127. Upper drive tape 125 and lower drive tape 127 canbe metal tapes that elastically deform when bent around a pulley. Upperdrive tape 125 and lower drive tape 127 are configured to withstand veryhigh frequency motion bending cycles. It should be appreciated thatupper drive tape 125 and lower drive tape 127 can be of any material orcombination of materials that are able to withstand a high number ofbending cycles. For example, upper drive tape 125 and lower drive tape127 can be formed with 17-7 TH1050 stainless steel and have a thicknessof approximately 0.004 inch.

Referring in particular to FIGS. 7 and 8, a first end portion of upperdrive tape 125 is coupled to a second bearing 131 such that a portion ofupper drive tape 125 is in contact with a radial surface of secondbearing 131. The second end portion of upper drive tape 125 is coupledto a lower portion 163 b of coupler 135. Upper drive tape 125 is incontact with a radial portion of first bearing 129 before partiallywrapping around a radial portion 155 of coupler 135 and being coupled toa lower portion 163 b. Similarly, a first end portion of lower drivetape 127 is coupled to second bearing 131 such that a portion of lowerdrive tape 127 is in contact with a radial surface of second bearing131. The second end portion of lower drive tape 127 is coupled to anupper portion 163 a of coupler 135. Lower drive tape 127 is in contactwith a radial portion of first bearing 129 before partially wrappingaround radial portion 155 of coupler 135 and being coupled to a upperportion 163 a. It should be appreciated that even though first bearing129 and second bearing 131 are illustrated as cylindrically shaped,first bearing 129 and second bearing 131 can have other shapes, such asa cam shape, for example. First bearing 129 and second bearing 131preferably are positioned to place upper drive tape 125 and lower drivetape 127 in tension. Upper drive tape 125 and lower drive tape 127 areconfigured so that they don't physically overlap each other. In theillustrated embodiment, openings in upper drive tape 125 and lower drivetape 127 allows each to partially wrap around first bearing 129 andattach to coupler 135 without contacting each other.

During operation, inboard frame 119 is actuated reciprocally indirections 159 a and 159 b, while outboard frame 121 is actuatedreciprocally in directions 161 a and 161 b. A translation of inboardframe 119 in direction 159 a causes coupler 135 to be pulled in anupward direction 163 a by upper drive tape 125. Conversely, atranslation of outboard frame 121 in direction 161 a causes coupler 135to be pulled in a downward direction 163 b by lower drive tape 127. Aratio between a radius R1 of radial portion 155 of coupler 135 and theouter radius of first bearing 129 forms the mechanical advantage of thetransmission of actuation system 115. In such a configuration, linearactuators 123 a-123 d move the flexible drive tapes 125 and 127 whichdirectly displaces the flap input lever 133 that is coupled to coupler135. The magnitude and frequency of the reciprocal translations offrames 119 and 121 can be selectively controlled during operation.

One advantage of the configuration of actuation system 115 is thatinboard frame 119 and outboard frame 121 translate in opposite chordwisedirections such that the inertial forces reactions cancel each other,resulting in a system that is not adversely affected by chordwiseaccelerations of the rotor blade that can occur during operation of theaircraft. For example, lead/lag accelerations are an example ofchordwise accelerations of the rotor blade that can be manifest duringoperation of the aircraft. The unique configuration of actuation system115 allows it to be substantially unaffected by such lead/lagaccelerations.

Referring now also to FIGS. 9 and 10, inboard frame 119 is illustratedin further detail. It should be appreciated that outboard frame 121 issubstantially similar to inboard frame 119, and that for the sake ofconciseness only inboard frame 119 is shown in FIGS. 9 and 10. Inboardframe 119 is configured to have considerable stiffness and strength toreact operational loading and prevent the operational loading frommanifesting as deflection where extension 151 is coupled to upper drivetape 125. Deflection of inboard frame 119 could otherwise distort upperdrive tape 125 during operation, so as to undesirably reduce the fatiguelife of upper drive tape 125.

Inboard frame 119 can be an assembly of composite members and layersconfigured for rigidly transferring linear displacements of actuators123 a and 123 b to upper drive tape 125. Inboard frame 119 can include afull pocket 193 and a partial pocket 195 sized to accommodate actuators123 a and 123 b, thereby forming a brace member 201 extending betweenarms 203 a and 203 b. It should be appreciated that inboard frame 119can be modified to accommodate a greater or fewer number of actuators.In an alternative embodiment, inboard frame 119 can include a fullpocket in lieu of partial pocket 195, thereby forming an additionalbrace member.

Inboard frame 119 can include an upper plate 177 and a lower plate 179,each having multidirectional fibers embedded in a resin matrix. A centerplate 181 can be located at the center between upper plate 177 and lowerplate 179. Tracks 185 a-185 d are formed with unidirectional fiberswound in a racetrack pattern thereby forming full pocket 193therewithin. Similarly, tracks 187 a-187 d are formed withunidirectional fibers wound in a racetrack pattern, but subsequentlytrimmed in half to form the geometry of partial pocket 195. An outermember 183 can be included around the exterior. Upper shoe layer 197 andlower shoe layer 199 are formed with unidirectional fibers wound in aracetrack pattern, but also subsequently trimmed to form a horseshoeshaped layer.

Extension 151 can include a filler 191 enclosed by a shell 189. In theillustrated embodiment, filler 191 is a closed-cell foam filler that istrimmed to the desired shape. Shell 189 is a multidirectional compositemember that encloses filler 191 to form a rigid torsion box. Shell 189and filler 191 are butt jointed to outer member 183. Upper plate 177 andlower plate 179 add rigidity by providing a shear support path betweentorsion box shell 189 and tracks 185 a-185 d and tracks 187 a-187 d.

It should be appreciated that even though extension 151 forms atrapezoidal shape cross-section shape, extension 151 may be configuredin other shapes that also perform rigidly in torsion and bending. Forexample, extension can form a square or rectangular shape.

Inboard frame 119 and outboard frame 121 are configured to act stiff intorsion and bending so that operational loading does not result indeflection at extension 151. Deflection of extension 151 is undesirablebecause it could result in a wrinkling of upper drive tape 125 and lowerdrive tape 127, thereby reducing fatigue life.

Referring now also to FIGS. 11-13, flap mechanism 117 is described infurther detail. Flap mechanism 117 can include a clevis 165 that isrigidly coupled to flap 113. Clevis 165 slidingly engages flap inputlever 133 such that rotational inputs from flap input lever 133 resultin rotational movements of flap 113 about a hinge axis 167. Clevis 165is configured such that spanwise operational loads, such as centrifugalforces, are not reacted between clevis 165 and flap input lever 133.Rather, centrifugal forces are reacted by a tension-torsion member 171that is support by an inboard support 173 and an outboard support 175.Inboard support 173 is fixed relative to rotor blade 105. In theillustrated embodiment, inboard support 173 is coupled to a fixedportion of a hinge assembly 169. Outboard support 175 is fixed relativeto flap 113. During operation, tension-torsion member 171 is compliantin torsion to allow for the relative rotation between flap 113 and rotorblade 105. Furthermore, tension-torsion member 171, under tension,stretches in the spanwise direction when reacting centrifugal loads thatact upon flap 113. In such a configuration, neither clevis 165, flapinput lever 133, nor hinge assembly 169 react the centrifugal loads.Hinge assembly 169, as well as any other hinges between flap 113 androtor blade 105, is configured with slack in the spanwise direction sothat a spanwise movement of flap 113 is not reacted by hinge assembly169, or other hinges defining hinge axis 167. One benefit is that thisconfiguration of flap mechanism 117 prevents centrifugal loads fromcausing a spanwise deflection of flap input lever 133 and coupler 135,thereby preventing an undesired wrinkling of upper drive tape 125 andlower drive tape 127.

In the illustrated embodiment, tension-torsion member 171 is a compositeband member with fiberglass fibers oriented unidirectionally along thelengthwise axis in a racetrack type configuration; however, the exactcomposite material and fiber orientation is implementation specific. Itshould be appreciated that tension-torsion member 171 can bemanufactured with a variety of suitable materials. Furthermore,alternative embodiments of tension-torsion member 171 can includemechanical assemblies configured to react centrifugal loads while beingcompliant in torsion. Such an alternative embodiment can include acylindrical rod assembly having a bearing, such as an elastomericbearing, that exhibits the desired tension and torsion properties.

During operation of rotorcraft 101, a control system is configured tocommand actuation system 115 to actuate flap 113 at a desired frequencyand displacement. Actuation system 115 is configured to provide angulardisplacement of flap 113 of up to positive 10 degrees and negative 10degrees, for example. Further, actuation system 115 is configured toprovide actuation frequencies at least from zero to 30 hertz, forexample. The angular displacement and frequency can be continuouslychanged during operation. Further, actuation system 115 can be operatedto provide a large angular displacement at a low frequency (such as onceper blade revolution) and low displacements at a high frequency (such as6 times per blade revolution). The displacement and frequency can becontinuously adjusted to achieve one or more desirables, such asvibration reduction, aircraft hover performance, aircraft speedperformance, and/or aircraft fuel efficiency, to name a few examples.

The systems of the present application include one or more significantadvantages over conventional systems, such as: 1) the actuation systemhas high bandwidth and large displacement; 2) the actuation system hasframes that move in opposite directions so as to negate chordwiseloading of the rotor blade; 3) the flap mechanism allows the spanwiseposition of the flap to float, thereby preventing centrifugal loadingfrom being reacted by the actuation system; 4) the actuation system doesnot protrude from the normal aerodynamic profile of the rotor blade; 5)the actuation system has a long fatigue life; 6) the actuation systemand flap mechanism are scalable to larger and smaller rotor blades; 7)the actuation system can incorporate multiple actuators for redundancy;and 8) the actuation system is resistant to the formation of backlash.

The particular embodiments disclosed above are illustrative only, as thesystem may be modified and practiced in different but equivalent mannersapparent to those skilled in the art having the benefit of the teachingsherein. Modifications, additions, or omissions may be made to theapparatuses described herein without departing from the scope of theinvention. The components of the system may be integrated or separated.Moreover, the operations of the system may be performed by more, fewer,or other components.

Furthermore, no limitations are intended to the details of constructionor design herein shown, other than as described in the claims below. Itis therefore evident that the particular embodiments disclosed above maybe altered or modified and all such variations are considered within thescope and spirit of the application. Accordingly, the protection soughtherein is as set forth in the claims below.

To aid the Patent Office, and any readers of any patent issued on thisapplication in interpreting the claims appended hereto, applicants wishto note that they do not intend any of the appended claims to invokeparagraph 6 of 35 U.S.C. §112 as it exists on the date of filing hereofunless the words “means for” or “step for” are explicitly used in theparticular claim.

The invention claimed is:
 1. A flap mechanism configured for translatinga moveable airfoil surface on a rotor blade, the flap mechanismcomprising: an input lever that is rotatable about a rotational axis,the input lever being coupled to an upper drive tape and a lower drivetape, the upper drive tape and the lower drive tape each beingelastically deformable and configured to alternately pull the inputlever so that the input lever reciprocally rotates about the rotationalaxis; and a clevis fitting fixed to the moveable airfoil surface, theclevis fitting also being slidingly coupled to the input lever such thatthe clevis fitting allows a translation of the moveable airfoil surfacein a spanwise direction relative to the input lever, such that arotational input from the input lever causes the moveable airfoilsurface to rotate about the rotational axis.
 2. The flap mechanismaccording to claim 1, further comprising: a hinge assembly defining therotational axis.
 3. The flap mechanism according to claim 1, furthercomprising: a tension-torsion member coupled to a rotor blade structureand the moveable airfoil surface, the tension-torsion member beingconfigured to react centrifugal forces experienced by the moveableairfoil surface.
 4. The flap mechanism according to claim 3, wherein thetension-torsion member is a composite band member.
 5. The flap mechanismaccording to claim 3, wherein the tension-torsion member is a compositeband member with fibers oriented in a unidirectional pattern.
 6. Theflap mechanism according to claim 3, wherein the tension-torsion memberis configured to torsionally twist when the moveable airfoil surface isrotated about the rotational axis.
 7. The flap mechanism according toclaim 3, wherein the tension-torsion member is coupled to the moveableairfoil surface with an outboard support.
 8. The flap mechanismaccording to claim 3, wherein the tension-torsion member is coupled tothe rotor blade structure with an inboard support.
 9. The flap mechanismaccording to claim 1, wherein the moveable airfoil surface is a trailingedge flap.
 10. The flap mechanism according to claim 1, wherein theclevis fitting includes an upper arm positioned above the input leverand a lower arm positioned below the input lever.
 11. A rotor bladehaving a moveable airfoil member, the rotor blade comprising: a root endand a tip end that define a spanwise direction therebetween; a leadingedge and a trailing edge that define a chordwise direction therebetween;an actuation system comprising: a first bearing and a second bearing; anupper drive tape and a lower drive tape, wherein each of the upper drivetape and the lower drive tape is elastically deformable; a first linearactuator and a second linear actuator; an inboard frame operablyassociated with the first linear actuator, the inboard frame beingcoupled to the upper drive tape; an outboard frame operably associatedwith the second linear actuator, the outboard frame being coupled to thelower drive tape; a flap mechanism comprising: an input lever coupled tothe upper drive tape and the lower drive tape, the input lever beingrotatable about a rotational axis; a clevis fitting fixed to themoveable airfoil member, the clevis fitting also being slidingly engagedto the input lever such that the clevis fitting allows a translation ofthe moveable airfoil member in the spanwise direction relative to theinput lever, but that a rotational input from the input lever causes themoveable airfoil member to rotate about the rotational axis; wherein areciprocal translation of the first frame and the second frame resultsin a reciprocal movement of the input lever.
 12. The rotor bladeaccording to claim 11, the flap mechanism further comprising: a hingeassembly defining the rotational axis of the moveable airfoil member.13. The rotor blade according to claim 11, the flap mechanism furthercomprising: a tension-torsion member coupled to a rotor blade structureand the moveable airfoil member, the tension-torsion member beingconfigured to react centrifugal forces experienced by the moveableairfoil member.
 14. The rotor blade according to claim 13, wherein thetension-torsion member is a composite band member.
 15. The rotor bladeaccording to claim 13, wherein the tension-torsion member is configuredto torsionally twist when the moveable airfoil member is rotated aboutthe rotational axis.
 16. The rotor blade according to claim 11, whereinthe moveable airfoil member is a trailing edge flap.
 17. The rotor bladeaccording to claim 11, wherein the clevis fitting includes an upper armpositioned above the input lever and a lower arm positioned below theinput lever.
 18. The rotor blade according to claim 11, the actuationsystem further comprising: a coupler member configured for coupling theupper drive tape and the lower drive tape to the input lever.